Many over snow vehicles can only be used for that purpose. There is a need for conversion units that can convert wheeled vehicles to effective over snow vehicles.
U.S. Pat. No. 3,710,886 discloses a conversion kit with a track for each side of a vehicle and the use of the brakes for steering. The track passes over a series of rollers.
U.S. Pat. No. 4,069,883 discloses a street car conversion with front skis for steering and a rear track for propulsion.
U.S. Pat. No. 4,313,516 discloses a similar arrangement which uses a chain drive from the rear wheels for the track. The tracks use rollers to support the track belt.
U.S. Pat. No. 4,719,882 is also a ski and track combination and takes its power from an extended drive shaft.
U.S. Pat. No. 5,855,248 discloses a kit that uses the existing wheels but is more for soft ground rather than snow.
Some patents have been concerned with farm tractor conversions.
U.S. Pat. No. 5,388,656 discloses a track for the road wheel of a tractor. U.S. Pat. No. 5,343,960 discloses a tracked conversion for a tractor that also uses an hydraulic steering attachment that is steered from the steering wheel. A single track is used on each side and the tracks pass over a horizontal slide when contacting the snow.
U.S. Pat. No. 5,361,860 discloses a track conversion where the steering is from attached trailing equipment.
U.S. Pat. No. 5,924,503 discloses a drive system for a tracked wheel.
U.S. Pat. No. 6,199,646 discloses a semi-crawler arrangement for the rear wheel of a farm tractor.
These prior art arrangements are generally unsatisfactory because the vehicle load on the snow is too high and the steering of the vehicle is non responsive or places the snow under too much shear so that propulsion over snow is inhibited. Eg: two directional shear when traversing, transverse, across a slope, one track moving faster than the other to prevent sideways slip, the effect being a torque onto the snow. All existing oversnow vehicles have a side slope maximum traverse angle of about thirteen degrees.
It is an object of this invention to provide a conversion for vehicles that ameliorates these problems